In a typical vehicle, a steering shaft extends from a steering wheel toward the front in order to transmit a steering torque of the steering wheel to wheels. For example, the steering shaft includes a shaft and a yoke fixed to a front end (leading end) portion of the shaft and partially constituting a coupling. The technique disclosed in Japanese Patent Application Laid-Open Publication No. H3-248727 is one of the conventional techniques pertaining to such an assembly of a shaft and a yoke.
In the assembly of the shaft and the yoke disclosed in Japanese Patent Application Laid-Open Publication No. H3-248727, the yoke is plugged on an end portion of the shaft. The end portion of the shaft penetrates through a main body of the yoke and faces the space between the arm portions of the yoke. The end portion of the shaft is caulked so as to expand toward the outer periphery. Caulking the end portion of the shaft prevents the yoke and the shaft from becoming disengaged from each other.